John perry



v Patented Nov. 21, 1893.

J. PERRY.

ELECTRIC METER.

(No Model.)

INVENTOR' WITNESSES:

UNITED STATES v PATENT OFFicE.

JOHN PERRY, OF LONDON, ENGLAND.

ELECTRIC METER.

SPECIFICATION forming part of Letters Patent No. 509,095, dated November 21, 1893.

Application filed March 28, 1893. Serialll'o. 467,968. (No model.) Patented in England March 14, 1891, No- 4,583; in France 1 November 27, 1891, No. 217,710, and in Belgium November 28, 1891, Ito- 97,380.

To all whom it may concern.- 1

Be itknown that I, J OHN PERRY, a subject of the Queen of Great Britain, residing at London,England, have invented certain new and useful Improvements in Electric Meters, (patented by me in Great Britain, No. 4,583, dated March 14, 1891; in France, N 0. 217,710, dated November 27, 1891, and in Belgium, No. 97,380, dated November 28, 1891,) of which the following is a full, clear, and exact de scription.

My invention relates to electric meters of that type in which the current to be measured flows between the edges and center of a cylindrical disk or other circular shaped armature, thereby causing the same to rotate in proportion to the current flowing.

The invention has special reference tothis type of meter, when the rotary parts move in contact with mercury through which the current also passes.

The object of the invention is to provide a construction which will be accurate and in which the amount of friction between the mercury and the armature will be small.

This invention is described in my English Patent'No. 4,583, dated March 14:, 1891.

The invention will be described in detail with reference to the accompanying drawings, in which- Figure 1 represents a vertical section of my improved meter. Fig. 2 is partial view of the meter, illustrating a modification thereof; and Fig. 3 is a transverse section on line as, a: of Fig. 1.

Referring to the drawings by letter, A represents a tubular electro-magnet through the coil of which a constant current flows which is preferably of sufficient quantity to maintain the iron slightly above the saturation point. The pole pieces of this magnet are cylindrical in shape and are represented by letters N and S. The pole faces are vertical and are provided with recesses or grooves n and s, respectively, standing opposite each other, thereby producing a field of force alternating in intensity throughout the entire space between the poles. This annular space between the poles is closed below by a copper ring a, in which there is a groove a registering with the said annular space. The upper end of the tubular magnet is covered by a disk I) of non-conducting material which is open at the center and between which and the pole piece N there is a horizontal space of substantially the same width as the annular space between the pole pieces. The groove in the ring, the space between the pole pieces, and'the horizontal space between the cover I) and the pole piece, form together an armature space in which is located a cylindrical armature c. This armature is continuous and its lower edge extends into the groove in the ring Ct. Its upper edge isconnectcd by a horizontal, integral web or disk with a vertical shaft 0. This shaft has its lower bearing in the center of the pole piece N, and extends upward through the opening in the cover I), and carries at its upper end a mercury cup 0 into which a rod 0 having a coincident axis, projects from above. In the lower end of this rod, the shaft 0 has its upper bearing, as shown. The rod is connected with a metallic cross-pieced, which is supported by, and insulated from, a frame 6. The mercury cup 0 contains mercury which maintains electrical contact between the cup and the rod. The entire armature space is also filled with mercury up to the level f, and it will be observed that the contact surface at the point where the armature shaft emerges from the mercury,is very small in comparison with what it is when the lower edge only of the armature is immersed; and it is this feature in electric meters when used in connection with two mercury cups, which constitutes my invention.

It will be observed that with two mercury cups separated and electrically connected by a shaft, as c, the entire current to be measured must flow through the armature, and none of it can shunt the armature by flowing through the mercury, as is the case when there is only one body of mercury and the current is delivered to the armature through the mercury at one end and leaves the armature through the mercury at the other end. The second or upper mercury cup, however, merely represents the location where the current is taken off, and while I prefer a mercury cup at that location, it is obvious that any other form of continuous contact may be utilized. The armature and spindle are provided on all their exposed surfaces with a coating of asphaltnm or other insulation, except at the lower edge of the armature where a belt is left bare. One terminal of the main carrying the current to be measured, is connected with the ring a, and the other terminal with the cross-piece d. If the positive terminal is attached to the ring a, the current will flow from the ring to the mercury, thence to the edge of the armature, thence through the armature to its center, then through the spindle to the mercury in cup 0 then to the rod 0 and finally to the cross-piece d. The current flowing from the edge of the cylindrical armature to its axis, will, in accordance with an established law, cause the armature to rotate in proportion to the current flowing.

The object of covering the armature with a coating of insulating material,is to prevent the current from entering the same at any other location than its edges.

Having thus described my invention, I claim 1. In an electric meter, a rotary shaft carrying at one end an armature entirely immersed in mercury, and at the other end making contact through mercury, in combination with an electric circuit, the terminals of which are respectively in said bodies of mercury, substantially as described.

2. In an electric meter, rotary shaft carrying at one end an armature entirely immersed in mercury, and at the other end making contact through mercury, in combination with an electric circuit, the terminals of which are respectively in said bodies of mercury, said armature being in the form of a cylinder, disk, or other circular body, and having its surface entirely insulated from the mercury in which it is immersed, except a narrow belt at its edge, substantially as described.

In testimony whereof I subscribe my signa ture in presence of two witnesses.

JOHN PERRY.

Witnesses:

GERALD F. BIRD, ARTHUR D. WALKER, Clerks to llfessrs. Come/ford 00., 7 Totem house Yard, Rothhm'y, E. (1, London. 

